In a manufacturing facility for semiconductor devices, there is a demand for improvement of a throughput for the purpose of increasing an operation rate of a polishing apparatus. The polishing apparatus includes a film-thickness measuring device for measuring a film thickness of a polished wafer in order to judge whether or not the wafer has been properly polished. Of all wafers, only some wafers, which have been designated in advance, are subjected to the film-thickness measurement, because it takes a certain time to measure the film thickness. For example, only a first wafer, a fifth wafer, and a tenth wafer are transported to the film-thickness measuring device, where the film thickness is measured.
In leading-edge processes of manufacturing semiconductor devices, improvement of a yield is also an important issue. From this viewpoint, if an error has occurred when a wafer is being polished, it is required to re-polish that wafer in order to avoid scrapping of that wafer. Thus, film-thickness measurement data is used as an index for judging whether or not re-polishing of the wafer is necessary.
However, as described above, the film-thickness measurement is performed only on some wafers that have been designated in advance. An error can occur during polishing of a wafer that is not one of the designated wafers. In such a case, the film-thickness measurement data of the error wafer cannot be obtained, and as a result, it is not possible to judge whether or not re-polishing of the error wafer should be performed.